Polymer thin film transistors have potential applications as key elements of integrated circuits for optoelectronic devices based on solution processing to lower manufacturing cost. Polymer thin film transistors generally have lower electrical performance such as lower mobility than do their silicon counterparts such as crystalline silicon or polysilicon thin film transistors. Nevertheless, the electrical performance levels of polymer thin film transistors may be sufficient for many applications, particularly large-area devices such as active matrix liquid crystal display, electronic paper, and certain low-end microelectronics such as smart cards, radio frequency identification tags, and the like, where high switching speeds may not be required. For these applications, low cost is particularly important. One main approach to obtaining higher charge carrier mobility for polymer thin film transistors is to achieve higher degrees of structural order in the active semiconducting polymer layer. PCT WO 00/79617 A1 discloses the alignment of the polymer chains parallel to each other by bringing the polymer into a liquid-crystalline phase. There is a need, which the present invention addresses, for new techniques applicable to the fabrication of electronic devices to induce increased structural order in semiconducting polymers.
The following documents also may be relevant:
F. Brustolin et al., xe2x80x9cHighly Ordered Structures of Amphiphilic Polythiophenes in Aqueous Media,xe2x80x9d Macromolecules, Vol. 35, pp. 1054-1059 (published on web Jan. 3, 2002).
G. Dufresne et al., xe2x80x9cThermochromic and Solvatochromic Conjugated Polymers by Design,xe2x80x9d Macromolecules, Vol. 33, pp. 8252-8257 (published on web Sep. 30, 2000).
M. Leclerc, xe2x80x9cOptical and Electrochemical Transducers Based on Functionalized Conjugated Polymers, Adv. Mater., Vol. 11, No. 18, pp. 1491-1498 (1999).
Yiliang Wu et al., U.S. Ser. No. 10/273,896 filed on the same day as the present application).
The present invention is accomplished in embodiments by providing a process comprising:
creating a composition comprising a liquid and a self-organizable polymer at least partially dissolved in the liquid, resulting in dissolved polymer molecules;
reducing the solubility of the dissolved polymer molecules to induce formation of structurally ordered polymer aggregates in the composition;
depositing a layer of the composition including the structurally ordered polymer aggregates; and
drying at least partially the layer to result in a structurally ordered layer, wherein the structurally ordered layer is part of an electronic device and the structurally ordered layer exhibits increased charge transport capability.
There are also provided in embodiments a process comprising:
creating a composition comprising a liquid and a self-organizable polymer at least partially dissolved in the liquid, resulting in dissolved polymer molecules, wherein the polymer is polythiophene;
reducing the solubility of the dissolved polymer molecules to induce formation of structurally ordered polymer aggregates in the composition, wherein the reducing the solubility of the dissolved polymer molecules is accomplished by adding a different liquid that is less capable of dissolving the polymer than the liquid;
depositing a layer of the composition including the structurally ordered polymer aggregates; and
drying at least partially the layer to result in a structurally ordered layer, wherein the structurally ordered layer is part of an electronic device and the structurally ordered layer exhibits increased charge transport capability.
There are further provided in embodiments a thin film transistor comprising:
an insulating layer;
a gate electrode;
a structurally ordered semiconductor layer;
a source electrode; and
a drain electrode,
wherein the insulating layer, the gate electrode, the semiconductor layer, the source electrode, and the drain electrode are in any sequence as long as the gate electrode and the semiconductor layer both contact the insulating layer, and the source electrode and the drain electrode both contact the semiconductor layer,
wherein the semiconductor layer is prepared by a process comprising:
creating a composition comprising a liquid and a self-organizable polymer at least partially dissolved in the liquid, resulting in dissolved polymer molecules;
reducing the solubility of the dissolved polymer molecules to induce formation of structurally ordered polymer aggregates in the composition;
depositing a layer of the composition including the structurally ordered polymer aggregates; and
drying at least partially the layer resulting in the structurally ordered semiconductor layer, wherein the structural order of the semiconductor layer increases the charge transport capability of the semiconductor layer.